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Scott Kelly, NASA's 1-Year Space Twin, Returns Today

The first-ever yearlong mission aboard the International Space Station ends tonight, and you can watch its final moments live.

The first-ever yearlong mission aboard the International Space Station ends tonight, and you can watch its final moments live.

PHOTOS: Calluses to Klingons, ISS Astronaut Tells All

A Soyuz spacecraft carrying NASA astronaut Scott Kelly and cosmonauts Mikhail Kornienko and Sergey Volkov is scheduled to land on the steppes of Kazakhstan tonight (March 1) at 11:27 p.m. EST (0427 GMT and 10:27 a.m. local Kazakhstan time on March 2). You can watch the landing live at, courtesy of NASA TV; coverage begins at 10:15 p.m. EST (0315 GMT on March 2).

Kelly and Kornienko arrived at the International Space Station (ISS) in March 2015, embarking upon a 340-day space mission designed to help pave the way for future crewed journeys to Mars. Volkov is completing a more typical 5.5-month expedition; he arrived at the space station last September.

PHOTOS: These Astronauts are NASA's Longest-Duration Space Fliers

You can also watch several key events leading up to the spaceflyers' landing today, courtesy of NASA TV as well: The hatches between the trio's Soyuz and the ISS are scheduled to close at 4:40 p.m. EST (2140 GMT), and the Soyuz is due to undock from the orbiting lab at 8:05 p.m. EST (0105 GMT on March 2).

Tonight's landing will end Kelly and Kornienko's year in space, but there's still much work to be done on the mission. Scientists will continue studying the duo to assess how their extended orbital stay affected them psychologically and physiologically.

Some of this work will involve comparing Scott Kelly to his identical twin brother, Mark, himself a former NASA astronaut. Kelly stayed on the ground to serve as a sort of genetic control for Scott.

PHOTOS: Astronaut Gets Stunning View of East Coast Blizzard

Kelly and Kornienko's 340-day mission has set an International Space Station mark, but they're about 100 days short of the all-time record for continuous space stays. Cosmonaut Valeri Polyakov lived aboard Russia's Mir space station for more than 437 days in 1994-95.

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In a series of photographs taken on March 1, Scott Kelly captured the sun rising over the limb of the Earth on his final day in space. "Rise and shine! My last #sunrise from space then I gotta go! #GoodMorning from @space_station! #YearInSpace," he tweeted.

Scott Kelly is a NASA astronaut working for a year in space on the International Space Station. Does he have the stuff of "The Martian,"

the highly anticipated Matt Damon movie to be released on Oct. 2

, chronicling the life of a stranded astronaut on the surface of Mars? While Kelly certainly isn't on his own in space, much of the work he is doing would be useful for a trip to Mars. Here are some of the things the astronaut is working on that Mark Watney (Damon's character in "The Martian") would appreciate.

MORE: NASA's Ultimate Space Twin Experiment

The sun goes through an 11-year cycle of activity, and we are just past the peak of one of those cycles. The solar peak is a time when the sun unleashes more flares and coronal mass ejections (charged particles). When these particles hit the Earth's magnetic field, they can produce spectacular auroras.

But they also can give astronauts a higher dose of radiation.

The space station monitors radiation levels for astronauts close to Earth; in fact, one of the reasons Kelly was selected for this mission was he did not exceed the lifetime radiation levels allowed for astronauts. Radiation is expected to jump for those travelling outside of Earth's magnetic influence. Mars doesn't have much magnetic field to speak of, and the Curiosity mission is monitoring radiation levels on the surface to get more information for future human missions.

MORE: Killer Radiation: How to Protect Martian Astronauts

Working in space is a harsh business. You're busy all the time, you're stuck in a small environment with several people, and your family and friends are far away. NASA keeps close tabs on its astronauts' psychological health through measures such as doctor calls with astronauts, and

having the astronauts keep journals

during their missions. This will especially be important for Mars, as astronauts will need to be even more self-sufficient due to the time delay in communications between planets. NASA has

an ongoing comm delays study

for astronauts doing simple tasks; these tasks and their effects on astronauts will be studied as the station work continues.

MORE: Space Radiation May Harm Astronauts' Brains

Microgravity is hard on your body. NASA has its astronauts exercise for a couple of hours a day, which seems to help counteract bone loss for missions of six months. But what about a year, or longer? That's part of what Kelly's mission is supposed to answer. Bones aren't the only things to worry about, either. Muscles shrink, eye pressure increases, your sense of balance changes. Even your immune system may be affected, something that

NASA is also looking at

in detail. So while we think of astronauts as boldly doing spacewalks and experiments on station, understand that they are also part of the experiment. Their very health is being watched for the benefit of future space missions.

MORE: Space Missions Turn Astronauts' Hearts Spherical

While Watney develops a certain affection for potatoes, Kelly recently posted a picture of himself looking pretty pleased next to a floating pile of fruit. It turns out that little comforts do go a long way for astronaut morale, and any nutritionist would tell you that a varied diet of healthy foods is good for you -- not just the freeze-dried stuff the Apollo astronauts survived on during their missions. NASA has an experiment in place to see how well

astronauts are meeting nutritional requirements for their work on station

, and also for their long-term health.

MORE: Real NASA Space Tech in 'The Martian'

Astronauts are very tied to shipments from Earth right now in terms of eating ... but that is changing in a small way.

Thanks to an experiment called Veggie

, astronauts got to taste some food grown aboard the space station this summer. Lettuce, of course, does not an entire meal make. But as the movie Contact (1997) reminds us, it's through "small moves" that we learn about science. The hope is eventually this experiment will translate into a better way of harvesting crops beyond Earth. For Mars, we're even wondering how viable the soil could be to support plants.

MORE: 'Smart' LED Farming Could Make Space Veg Viable

"#ILookLikeAnEngineer on @space_station. Also a scientist, medical officer, farmer & at times a plumber," Kelly wrote with this image in August. What's more, he has to do all those things in a small space. Since every pound hoisted to space costs money, astronauts are accustomed to working in claustrophobic quarters. But NASA, concerned about its astronauts' efficiency and happiness, also has an

experiment that is supposed to look at how best to construct a living space for astronauts

. That way, the habitats designed for Mars will be suitable for long-term living.

MORE: Why 'Space Madness' Fears Haunted NASA's Past

During a recent Twitter chat, Kelly was asked if he wanted to go to Mars. He said yes, as long as he could return. Getting to Mars and back will take hundreds of days of transportation, let alone the time on the surface. The gravity on Mars is less than 40% what we experience here on Earth. And unless spacecraft design changes substantially, the astronauts will be in microgravity on the way there and back. NASA has an experiment to see

how well (or badly) astronauts work on the surface shortly after landing

, an experiment that Kelly is participating in. This will be important not only for returning to Earth, but seeing how well a crew can get adapted to Mars after being in microgravity for the transit.

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